Soft tissues, such as ligaments, tendons and muscles, are attached to a large portion of the human skeleton. In particular, many ligaments and tendons are attached to the bones which form joints, such as shoulder and knee joints. A variety of injuries and conditions require attachment or reattachment of a soft tissue to bone. For example, when otherwise healthy tissue has been torn away from a bone, surgery is often required to reattach the tissue to the bone to allow healing and a natural reattachment to occur.
A number of devices and methods have been developed to attach soft tissue to bone. These include screws, staples, cement, suture anchors, and sutures alone. Some of the more successful methods involve use of a suture anchor to attach a suture to the bone, and tying the suture in a manner that holds the tissue in close proximity to the bone.
The tissue may be attached to the bone during open surgery, or during closed (e.g., arthroscopic) surgical procedures. Closed surgical procedures are preferred since they are less invasive and are less likely to cause patient trauma. In a closed surgical procedure, the surgeon performs diagnostic and therapeutic procedures at the surgical site through small incisions, called portals, using instruments specially designed for this purpose. One problem encountered in the less invasive, closed surgical procedures is that the surgeon has significantly less room to perform the required manipulations at the surgical site. Thus, devices and methods are needed which will allow a surgeon to effectively and easily attach tissue to bone in the small spaces provided by less invasive surgical procedures.
Conventional methods for attaching soft tissue to bone typically require that the surgeon tie a knot in the suture thread to attach the suture to an anchor, or to attach the tissue to the bone using the suture. Knot tying at the surgical site in closed surgical procedures, and even in open surgery, is difficult and time consuming due to inherent space constraints. As a result, certain knotless anchor systems have been developed to enhance surgeon convenience.
U.S. Pat. No. 5,569,306 provides one example of a knotless suture anchor system. A further knotless suture anchor and system is disclosed in U.S. Pat. No. 5,782,864. Although generally useful, such systems can be limited to use only with certain types or shapes of tissue, or to use with certain anatomical structures. Proper attachment of soft tissue requires that it be placed in the anatomically correct position to promote optimal healing.
Further, some conventional knotless suture anchor systems may require, in order to attach a broader array of tissue shapes to bone, that the suture anchor pass though the tissue to be attached. This is undesirable because it unnecessarily irritates the injured tissue and it requires opening a much larger hole in the tissue.
In some instances, however, it is still desirable to use a suture anchor system that requires that a suture knot be tied.
Some suture anchor systems, both those that are knotless and those that require a suture knot to be tied, rely on a sliding interface between a portion of the operative suture and the suture anchor. Excessive friction between the suture anchor and the operative suture can cause abrasion of the suture. Such abrasion can lead to fraying or even failure of the suture. Some suture anchor systems have been designed to include suture sleeves or buttresses that engage the suture and reduce the risk of suture abrasion. See, for example, U.S. Pat. Nos. 5,860,978 and 6,156,056. However, it would be desirable to provide alternative suture anchor systems in which the suture is less subject to frictional wear.
In addition to the previously mentioned need for a knotless anchoring system, there is thus a need for an improved system for anchoring soft tissue to bone which reduces the sliding friction between the anchor and the operative suture during the surgical procedure. Further, there is a need for an improved system for anchoring soft tissue to hard bone which is easy and fast to deploy and requires few tools. It would also be advantageous to provide a fully absorbable knotless suture anchor and system.